//
// Copyright(c) 2015 Gabi Melman.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
//

#pragma once

#include "spdlog/details/fmt_helper.h"
#include "spdlog/details/log_msg.h"
#include "spdlog/details/os.h"
#include "spdlog/fmt/fmt.h"
#include "spdlog/formatter.h"

#include <array>
#include <chrono>
#include <ctime>
#include <cctype>
#include <memory>
#include <mutex>
#include <string>
#include <thread>
#include <utility>
#include <vector>

namespace spdlog {
    namespace details {

// padding information.
        struct padding_info {
            enum pad_side {
                left,
                right,
                center
            };

            padding_info() = default;
            padding_info(size_t width, padding_info::pad_side side)
                : width_(width)
                , side_(side) {
            }

            bool enabled() const {
                return width_ != 0;
            }
            const size_t width_ = 0;
            const pad_side side_ = left;
        };

        class scoped_pad {
          public:
            scoped_pad(size_t wrapped_size, padding_info &padinfo, fmt::memory_buffer &dest)
                : padinfo_(padinfo)
                , dest_(dest) {

                if (padinfo_.width_ <= wrapped_size) {
                    total_pad_ = 0;
                    return;
                }

                total_pad_ = padinfo.width_ - wrapped_size;
                if (padinfo_.side_ == padding_info::left) {
                    pad_it(total_pad_);
                    total_pad_ = 0;
                } else if (padinfo_.side_ == padding_info::center) {
                    auto half_pad = total_pad_ / 2;
                    auto reminder = total_pad_ & 1;
                    pad_it(half_pad);
                    total_pad_ = half_pad + reminder; // for the right side
                }
            }

            scoped_pad(spdlog::string_view_t txt, padding_info &padinfo, fmt::memory_buffer &dest)
                : scoped_pad(txt.size(), padinfo, dest) {
            }

            ~scoped_pad() {
                if (total_pad_) {
                    pad_it(total_pad_);
                }
            }

          private:
            void pad_it(size_t count) {
                // count = std::min(count, spaces_.size());
                assert(count <= spaces_.size());
                fmt_helper::append_string_view(string_view_t(spaces_.data(), count), dest_);
            }

            const padding_info &padinfo_;
            fmt::memory_buffer &dest_;
            size_t total_pad_;
            string_view_t spaces_{"                                                                "
                "                                                                ",
                128};
        };

        class flag_formatter {
          public:
            explicit flag_formatter(padding_info padinfo)
                : padinfo_(padinfo) {
            }
            flag_formatter() = default;
            virtual ~flag_formatter() = default;
            virtual void format(const details::log_msg &msg, const std::tm &tm_time, fmt::memory_buffer &dest) = 0;

          protected:
            padding_info padinfo_;
        };

///////////////////////////////////////////////////////////////////////
// name & level pattern appender
///////////////////////////////////////////////////////////////////////
        class name_formatter : public flag_formatter {
          public:
            explicit name_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (padinfo_.enabled()) {
                    scoped_pad p(*msg.logger_name, padinfo_, dest);
                    fmt_helper::append_string_view(*msg.logger_name, dest);
                } else {
                    fmt_helper::append_string_view(*msg.logger_name, dest);
                }
            }
        };

// log level appender
        class level_formatter : public flag_formatter {
          public:
            explicit level_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                string_view_t &level_name = level::to_string_view(msg.level);
                if (padinfo_.enabled()) {
                    scoped_pad p(level_name, padinfo_, dest);
                    fmt_helper::append_string_view(level_name, dest);
                } else {
                    fmt_helper::append_string_view(level_name, dest);
                }
            }
        };

// short log level appender
        class short_level_formatter : public flag_formatter {
          public:
            explicit short_level_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                string_view_t level_name{level::to_short_c_str(msg.level)};
                scoped_pad p(level_name, padinfo_, dest);
                fmt_helper::append_string_view(level_name, dest);
            }
        };

///////////////////////////////////////////////////////////////////////
// Date time pattern appenders
///////////////////////////////////////////////////////////////////////

        static const char *ampm(const tm &t) {
            return t.tm_hour >= 12 ? "PM" : "AM";
        }

        static int to12h(const tm &t) {
            return t.tm_hour > 12 ? t.tm_hour - 12 : t.tm_hour;
        }

// Abbreviated weekday name
        static const char *days[] {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
        class a_formatter : public flag_formatter {
          public:
            explicit a_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                string_view_t field_value{days[tm_time.tm_wday]};
                scoped_pad p(field_value, padinfo_, dest);
                fmt_helper::append_string_view(field_value, dest);
            }
        };

// Full weekday name
        static const char *full_days[] {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};
        class A_formatter : public flag_formatter {
          public:
            explicit A_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                string_view_t field_value{full_days[tm_time.tm_wday]};
                scoped_pad p(field_value, padinfo_, dest);
                fmt_helper::append_string_view(field_value, dest);
            }
        };

// Abbreviated month
        static const char *months[] {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sept", "Oct", "Nov", "Dec"};
        class b_formatter : public flag_formatter {
          public:
            explicit b_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                string_view_t field_value{months[tm_time.tm_mon]};
                scoped_pad p(field_value, padinfo_, dest);
                fmt_helper::append_string_view(field_value, dest);
            }
        };

// Full month name
        static const char *full_months[] {
            "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"
        };
        class B_formatter : public flag_formatter {
          public:
            explicit B_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                string_view_t field_value{full_months[tm_time.tm_mon]};
                scoped_pad p(field_value, padinfo_, dest);
                fmt_helper::append_string_view(field_value, dest);
            }
        };

// Date and time representation (Thu Aug 23 15:35:46 2014)
        class c_formatter final : public flag_formatter {
          public:
            explicit c_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 24;
                scoped_pad p(field_size, padinfo_, dest);

                fmt_helper::append_string_view(days[tm_time.tm_wday], dest);
                dest.push_back(' ');
                fmt_helper::append_string_view(months[tm_time.tm_mon], dest);
                dest.push_back(' ');
                fmt_helper::append_int(tm_time.tm_mday, dest);
                dest.push_back(' ');
                // time

                fmt_helper::pad2(tm_time.tm_hour, dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_min, dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_sec, dest);
                dest.push_back(' ');
                fmt_helper::append_int(tm_time.tm_year + 1900, dest);
            }
        };

// year - 2 digit
        class C_formatter final : public flag_formatter {
          public:
            explicit C_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(tm_time.tm_year % 100, dest);
            }
        };

// Short MM/DD/YY date, equivalent to %m/%d/%y 08/23/01
        class D_formatter final : public flag_formatter {
          public:
            explicit D_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 10;
                scoped_pad p(field_size, padinfo_, dest);

                fmt_helper::pad2(tm_time.tm_mon + 1, dest);
                dest.push_back('/');
                fmt_helper::pad2(tm_time.tm_mday, dest);
                dest.push_back('/');
                fmt_helper::pad2(tm_time.tm_year % 100, dest);
            }
        };

// year - 4 digit
        class Y_formatter final : public flag_formatter {
          public:
            explicit Y_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 4;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::append_int(tm_time.tm_year + 1900, dest);
            }
        };

// month 1-12
        class m_formatter final : public flag_formatter {
          public:
            explicit m_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(tm_time.tm_mon + 1, dest);
            }
        };

// day of month 1-31
        class d_formatter final : public flag_formatter {
          public:
            explicit d_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(tm_time.tm_mday, dest);
            }
        };

// hours in 24 format 0-23
        class H_formatter final : public flag_formatter {
          public:
            explicit H_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(tm_time.tm_hour, dest);
            }
        };

// hours in 12 format 1-12
        class I_formatter final : public flag_formatter {
          public:
            explicit I_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(to12h(tm_time), dest);
            }
        };

// minutes 0-59
        class M_formatter final : public flag_formatter {
          public:
            explicit M_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(tm_time.tm_min, dest);
            }
        };

// seconds 0-59
        class S_formatter final : public flag_formatter {
          public:
            explicit S_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad2(tm_time.tm_sec, dest);
            }
        };

// milliseconds
        class e_formatter final : public flag_formatter {
          public:
            explicit e_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                auto millis = fmt_helper::time_fraction<std::chrono::milliseconds>(msg.time);
                if (padinfo_.enabled()) {
                    const size_t field_size = 3;
                    scoped_pad p(field_size, padinfo_, dest);
                    fmt_helper::pad3(static_cast<uint32_t>(millis.count()), dest);
                } else {
                    fmt_helper::pad3(static_cast<uint32_t>(millis.count()), dest);
                }
            }
        };

// microseconds
        class f_formatter final : public flag_formatter {
          public:
            explicit f_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                auto micros = fmt_helper::time_fraction<std::chrono::microseconds>(msg.time);
                if (padinfo_.enabled()) {
                    const size_t field_size = 6;
                    scoped_pad p(field_size, padinfo_, dest);
                    fmt_helper::pad6(static_cast<size_t>(micros.count()), dest);
                } else {
                    fmt_helper::pad6(static_cast<size_t>(micros.count()), dest);
                }
            }
        };

// nanoseconds
        class F_formatter final : public flag_formatter {
          public:
            explicit F_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                auto ns = fmt_helper::time_fraction<std::chrono::nanoseconds>(msg.time);
                if (padinfo_.enabled()) {
                    const size_t field_size = 9;
                    scoped_pad p(field_size, padinfo_, dest);
                    fmt_helper::pad9(static_cast<size_t>(ns.count()), dest);
                } else {
                    fmt_helper::pad9(static_cast<size_t>(ns.count()), dest);
                }
            }
        };

// seconds since epoch
        class E_formatter final : public flag_formatter {
          public:
            explicit E_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                const size_t field_size = 10;
                scoped_pad p(field_size, padinfo_, dest);
                auto duration = msg.time.time_since_epoch();
                auto seconds = std::chrono::duration_cast<std::chrono::seconds>(duration).count();
                fmt_helper::append_int(seconds, dest);
            }
        };

// AM/PM
        class p_formatter final : public flag_formatter {
          public:
            explicit p_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 2;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::append_string_view(ampm(tm_time), dest);
            }
        };

// 12 hour clock 02:55:02 pm
        class r_formatter final : public flag_formatter {
          public:
            explicit r_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 11;
                scoped_pad p(field_size, padinfo_, dest);

                fmt_helper::pad2(to12h(tm_time), dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_min, dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_sec, dest);
                dest.push_back(' ');
                fmt_helper::append_string_view(ampm(tm_time), dest);
            }
        };

// 24-hour HH:MM time, equivalent to %H:%M
        class R_formatter final : public flag_formatter {
          public:
            explicit R_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 5;
                scoped_pad p(field_size, padinfo_, dest);

                fmt_helper::pad2(tm_time.tm_hour, dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_min, dest);
            }
        };

// ISO 8601 time format (HH:MM:SS), equivalent to %H:%M:%S
        class T_formatter final : public flag_formatter {
          public:
            explicit T_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 8;
                scoped_pad p(field_size, padinfo_, dest);

                fmt_helper::pad2(tm_time.tm_hour, dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_min, dest);
                dest.push_back(':');
                fmt_helper::pad2(tm_time.tm_sec, dest);
            }
        };

// ISO 8601 offset from UTC in timezone (+-HH:MM)
        class z_formatter final : public flag_formatter {
          public:
            explicit z_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            const std::chrono::seconds cache_refresh = std::chrono::seconds(5);

            z_formatter() = default;
            z_formatter(const z_formatter &) = delete;
            z_formatter &operator=(const z_formatter &) = delete;

            void format(const details::log_msg &msg, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                const size_t field_size = 6;
                scoped_pad p(field_size, padinfo_, dest);

#ifdef _WIN32
                int total_minutes = get_cached_offset(msg, tm_time);
#else
                // No need to chache under gcc,
                // it is very fast (already stored in tm.tm_gmtoff)
                (void)(msg);
                int total_minutes = os::utc_minutes_offset(tm_time);
#endif
                bool is_negative = total_minutes < 0;
                if (is_negative) {
                    total_minutes = -total_minutes;
                    dest.push_back('-');
                } else {
                    dest.push_back('+');
                }

                fmt_helper::pad2(total_minutes / 60, dest); // hours
                dest.push_back(':');
                fmt_helper::pad2(total_minutes % 60, dest); // minutes
            }

          private:
            log_clock::time_point last_update_{std::chrono::seconds(0)};
#ifdef _WIN32
            int offset_minutes_ {0};

            int get_cached_offset(const log_msg &msg, const std::tm &tm_time) {
                if (msg.time - last_update_ >= cache_refresh) {
                    offset_minutes_ = os::utc_minutes_offset(tm_time);
                    last_update_ = msg.time;
                }
                return offset_minutes_;
            }
#endif
        };

// Thread id
        class t_formatter final : public flag_formatter {
          public:
            explicit t_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (padinfo_.enabled()) {
                    const auto field_size = fmt_helper::count_digits(msg.thread_id);
                    scoped_pad p(field_size, padinfo_, dest);
                    fmt_helper::append_int(msg.thread_id, dest);
                } else {
                    fmt_helper::append_int(msg.thread_id, dest);
                }
            }
        };

// Current pid
        class pid_formatter final : public flag_formatter {
          public:
            explicit pid_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &, const std::tm &, fmt::memory_buffer &dest) override {
                const auto pid = static_cast<uint32_t>(details::os::pid());
                if (padinfo_.enabled()) {
                    auto field_size = fmt_helper::count_digits(pid);
                    scoped_pad p(field_size, padinfo_, dest);
                    fmt_helper::append_int(pid, dest);
                } else {
                    fmt_helper::append_int(pid, dest);
                }
            }
        };

// message counter formatter
        class i_formatter final : public flag_formatter {
          public:
            explicit i_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                const size_t field_size = 6;
                scoped_pad p(field_size, padinfo_, dest);
                fmt_helper::pad6(msg.msg_id, dest);
            }
        };

        class v_formatter final : public flag_formatter {
          public:
            explicit v_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (padinfo_.enabled()) {
                    scoped_pad p(msg.payload, padinfo_, dest);
                    fmt_helper::append_string_view(msg.payload, dest);
                } else {
                    fmt_helper::append_string_view(msg.payload, dest);
                }
            }
        };

        class ch_formatter final : public flag_formatter {
          public:
            explicit ch_formatter(char ch)
                : ch_(ch) {
            }

            void format(const details::log_msg &, const std::tm &, fmt::memory_buffer &dest) override {
                const size_t field_size = 1;
                scoped_pad p(field_size, padinfo_, dest);
                dest.push_back(ch_);
            }

          private:
            char ch_;
        };

// aggregate user chars to display as is
        class aggregate_formatter final : public flag_formatter {
          public:
            aggregate_formatter() = default;

            void add_ch(char ch) {
                str_ += ch;
            }
            void format(const details::log_msg &, const std::tm &, fmt::memory_buffer &dest) override {
                fmt_helper::append_string_view(str_, dest);
            }

          private:
            std::string str_;
        };

// mark the color range. expect it to be in the form of "%^colored text%$"
        class color_start_formatter final : public flag_formatter {
          public:
            explicit color_start_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                msg.color_range_start = dest.size();
            }
        };
        class color_stop_formatter final : public flag_formatter {
          public:
            explicit color_stop_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                msg.color_range_end = dest.size();
            }
        };

// print source location
        class source_location_formatter final : public flag_formatter {
          public:
            explicit source_location_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (msg.source.empty()) {
                    return;
                }
                if (padinfo_.enabled()) {
                    const auto text_size = std::char_traits<char>::length(msg.source.filename) + fmt_helper::count_digits(msg.source.line) + 1;
                    scoped_pad p(text_size, padinfo_, dest);
                    fmt_helper::append_string_view(msg.source.filename, dest);
                    dest.push_back(':');
                    fmt_helper::append_int(msg.source.line, dest);
                } else {
                    fmt_helper::append_string_view(msg.source.filename, dest);
                    dest.push_back(':');
                    fmt_helper::append_int(msg.source.line, dest);
                }
            }
        };
// print source filename
        class source_filename_formatter final : public flag_formatter {
          public:
            explicit source_filename_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (msg.source.empty()) {
                    return;
                }
                scoped_pad p(msg.source.filename, padinfo_, dest);
                fmt_helper::append_string_view(msg.source.filename, dest);
            }
        };

        class source_linenum_formatter final : public flag_formatter {
          public:
            explicit source_linenum_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (msg.source.empty()) {
                    return;
                }
                if (padinfo_.enabled()) {
                    auto field_size = fmt_helper::count_digits(msg.source.line);
                    scoped_pad p(field_size, padinfo_, dest);
                    fmt_helper::append_int(msg.source.line, dest);
                } else {
                    fmt_helper::append_int(msg.source.line, dest);
                }
            }
        };
// print source funcname
        class source_funcname_formatter final : public flag_formatter {
          public:
            explicit source_funcname_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {};

            void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override {
                if (msg.source.empty() || msg.source.funcname == nullptr) {
                    return;
                }
                scoped_pad p(msg.source.funcname, padinfo_, dest);
                fmt_helper::append_string_view(msg.source.funcname, dest);
            }
        };

// Full info formatter
// pattern: [%Y-%m-%d %H:%M:%S.%e] [%n] [%l] %v
        class full_formatter final : public flag_formatter {
          public:
            explicit full_formatter(padding_info padinfo)
                : flag_formatter(padinfo) {
            }

            void format(const details::log_msg &msg, const std::tm &tm_time, fmt::memory_buffer &dest) override {
                using std::chrono::duration_cast;
                using std::chrono::milliseconds;
                using std::chrono::seconds;

#ifndef SPDLOG_NO_DATETIME

                // cache the date/time part for the next second.
                auto duration = msg.time.time_since_epoch();
                auto secs = duration_cast<seconds>(duration);

                if (cache_timestamp_ != secs || cached_datetime_.size() == 0) {
                    cached_datetime_.clear();
                    cached_datetime_.push_back('[');
                    fmt_helper::append_int(tm_time.tm_year + 1900, cached_datetime_);
                    cached_datetime_.push_back('-');

                    fmt_helper::pad2(tm_time.tm_mon + 1, cached_datetime_);
                    cached_datetime_.push_back('-');

                    fmt_helper::pad2(tm_time.tm_mday, cached_datetime_);
                    cached_datetime_.push_back(' ');

                    fmt_helper::pad2(tm_time.tm_hour, cached_datetime_);
                    cached_datetime_.push_back(':');

                    fmt_helper::pad2(tm_time.tm_min, cached_datetime_);
                    cached_datetime_.push_back(':');

                    fmt_helper::pad2(tm_time.tm_sec, cached_datetime_);
                    cached_datetime_.push_back('.');

                    cache_timestamp_ = secs;
                }
                fmt_helper::append_buf(cached_datetime_, dest);

                auto millis = fmt_helper::time_fraction<milliseconds>(msg.time);
                fmt_helper::pad3(static_cast<uint32_t>(millis.count()), dest);
                dest.push_back(']');
                dest.push_back(' ');

#else // no datetime needed
                (void)tm_time;
#endif

#ifndef SPDLOG_NO_NAME
                if (!msg.logger_name->empty()) {
                    dest.push_back('[');
                    // fmt_helper::append_str(*msg.logger_name, dest);
                    fmt_helper::append_string_view(*msg.logger_name, dest);
                    dest.push_back(']');
                    dest.push_back(' ');
                }
#endif

                dest.push_back('[');
                // wrap the level name with color
                msg.color_range_start = dest.size();
                // fmt_helper::append_string_view(level::to_c_str(msg.level), dest);
                fmt_helper::append_string_view(level::to_string_view(msg.level), dest);
                msg.color_range_end = dest.size();
                dest.push_back(']');
                dest.push_back(' ');

                // add source location if present
                if (!msg.source.empty()) {
                    dest.push_back('[');
                    fmt_helper::append_string_view(msg.source.filename, dest);
                    dest.push_back(':');
                    fmt_helper::append_int(msg.source.line, dest);
                    dest.push_back(']');
                    dest.push_back(' ');
                }
                // fmt_helper::append_string_view(msg.msg(), dest);
                fmt_helper::append_string_view(msg.payload, dest);
            }

          private:
            std::chrono::seconds cache_timestamp_{0};
            fmt::basic_memory_buffer<char, 128> cached_datetime_;
        };

    } // namespace details

    class pattern_formatter final : public formatter {
      public:
        explicit pattern_formatter(
            std::string pattern, pattern_time_type time_type = pattern_time_type::local, std::string eol = spdlog::details::os::default_eol)
            : pattern_(std::move(pattern))
            , eol_(std::move(eol))
            , pattern_time_type_(time_type)
            , last_log_secs_(0) {
            std::memset(&cached_tm_, 0, sizeof(cached_tm_));
            compile_pattern_(pattern_);
        }

        // use by default full formatter for if pattern is not given
        explicit pattern_formatter(pattern_time_type time_type = pattern_time_type::local, std::string eol = spdlog::details::os::default_eol)
            : pattern_("%+")
            , eol_(std::move(eol))
            , pattern_time_type_(time_type)
            , last_log_secs_(0) {
            std::memset(&cached_tm_, 0, sizeof(cached_tm_));
            formatters_.push_back(details::make_unique<details::full_formatter>(details::padding_info{}));
        }

        pattern_formatter(const pattern_formatter &other) = delete;
        pattern_formatter &operator=(const pattern_formatter &other) = delete;

        std::unique_ptr<formatter> clone() const override {
            return details::make_unique<pattern_formatter>(pattern_, pattern_time_type_, eol_);
        }

        void format(const details::log_msg &msg, fmt::memory_buffer &dest) override {
#ifndef SPDLOG_NO_DATETIME
            auto secs = std::chrono::duration_cast<std::chrono::seconds>(msg.time.time_since_epoch());
            if (secs != last_log_secs_) {
                cached_tm_ = get_time_(msg);
                last_log_secs_ = secs;
            }
#endif
            for (auto &f : formatters_) {
                f->format(msg, cached_tm_, dest);
            }
            // write eol
            details::fmt_helper::append_string_view(eol_, dest);
        }

      private:
        std::string pattern_;
        std::string eol_;
        pattern_time_type pattern_time_type_;
        std::tm cached_tm_;
        std::chrono::seconds last_log_secs_;

        std::vector<std::unique_ptr<details::flag_formatter>> formatters_;

        std::tm get_time_(const details::log_msg &msg) {
            if (pattern_time_type_ == pattern_time_type::local) {
                return details::os::localtime(log_clock::to_time_t(msg.time));
            }
            return details::os::gmtime(log_clock::to_time_t(msg.time));
        }

        void handle_flag_(char flag, details::padding_info padding) {
            switch (flag) {

            case ('+'): // default formatter
                formatters_.push_back(details::make_unique<details::full_formatter>(padding));
                break;

            case 'n': // logger name
                formatters_.push_back(details::make_unique<details::name_formatter>(padding));
                break;

            case 'l': // level
                formatters_.push_back(details::make_unique<details::level_formatter>(padding));
                break;

            case 'L': // short level
                formatters_.push_back(details::make_unique<details::short_level_formatter>(padding));
                break;

            case ('t'): // thread id
                formatters_.push_back(details::make_unique<details::t_formatter>(padding));
                break;

            case ('v'): // the message text
                formatters_.push_back(details::make_unique<details::v_formatter>(padding));
                break;

            case ('a'): // weekday
                formatters_.push_back(details::make_unique<details::a_formatter>(padding));
                break;

            case ('A'): // short weekday
                formatters_.push_back(details::make_unique<details::A_formatter>(padding));
                break;

            case ('b'):
            case ('h'): // month
                formatters_.push_back(details::make_unique<details::b_formatter>(padding));
                break;

            case ('B'): // short month
                formatters_.push_back(details::make_unique<details::B_formatter>(padding));
                break;

            case ('c'): // datetime
                formatters_.push_back(details::make_unique<details::c_formatter>(padding));
                break;

            case ('C'): // year 2 digits
                formatters_.push_back(details::make_unique<details::C_formatter>(padding));
                break;

            case ('Y'): // year 4 digits
                formatters_.push_back(details::make_unique<details::Y_formatter>(padding));
                break;

            case ('D'):
            case ('x'): // datetime MM/DD/YY
                formatters_.push_back(details::make_unique<details::D_formatter>(padding));
                break;

            case ('m'): // month 1-12
                formatters_.push_back(details::make_unique<details::m_formatter>(padding));
                break;

            case ('d'): // day of month 1-31
                formatters_.push_back(details::make_unique<details::d_formatter>(padding));
                break;

            case ('H'): // hours 24
                formatters_.push_back(details::make_unique<details::H_formatter>(padding));
                break;

            case ('I'): // hours 12
                formatters_.push_back(details::make_unique<details::I_formatter>(padding));
                break;

            case ('M'): // minutes
                formatters_.push_back(details::make_unique<details::M_formatter>(padding));
                break;

            case ('S'): // seconds
                formatters_.push_back(details::make_unique<details::S_formatter>(padding));
                break;

            case ('e'): // milliseconds
                formatters_.push_back(details::make_unique<details::e_formatter>(padding));
                break;

            case ('f'): // microseconds
                formatters_.push_back(details::make_unique<details::f_formatter>(padding));
                break;

            case ('F'): // nanoseconds
                formatters_.push_back(details::make_unique<details::F_formatter>(padding));
                break;

            case ('E'): // seconds since epoch
                formatters_.push_back(details::make_unique<details::E_formatter>(padding));
                break;

            case ('p'): // am/pm
                formatters_.push_back(details::make_unique<details::p_formatter>(padding));
                break;

            case ('r'): // 12 hour clock 02:55:02 pm
                formatters_.push_back(details::make_unique<details::r_formatter>(padding));
                break;

            case ('R'): // 24-hour HH:MM time
                formatters_.push_back(details::make_unique<details::R_formatter>(padding));
                break;

            case ('T'):
            case ('X'): // ISO 8601 time format (HH:MM:SS)
                formatters_.push_back(details::make_unique<details::T_formatter>(padding));
                break;

            case ('z'): // timezone
                formatters_.push_back(details::make_unique<details::z_formatter>(padding));
                break;

            case ('P'): // pid
                formatters_.push_back(details::make_unique<details::pid_formatter>(padding));
                break;

#ifdef SPDLOG_ENABLE_MESSAGE_COUNTER
            case ('i'):
                formatters_.push_back(details::make_unique<details::i_formatter>(padding));
                break;
#endif
            case ('^'): // color range start
                formatters_.push_back(details::make_unique<details::color_start_formatter>(padding));
                break;

            case ('$'): // color range end
                formatters_.push_back(details::make_unique<details::color_stop_formatter>(padding));
                break;

            case ('@'): // source location (filename:filenumber)
                formatters_.push_back(details::make_unique<details::source_location_formatter>(padding));
                break;

            case ('s'): // source filename
                formatters_.push_back(details::make_unique<details::source_filename_formatter>(padding));
                break;

            case ('#'): // source line number
                formatters_.push_back(details::make_unique<details::source_linenum_formatter>(padding));
                break;

            case ('!'): // source funcname
                formatters_.push_back(details::make_unique<details::source_funcname_formatter>(padding));
                break;

            case ('%'): // % char
                formatters_.push_back(details::make_unique<details::ch_formatter>('%'));
                break;

            default: // Unknown flag appears as is
                auto unknown_flag = details::make_unique<details::aggregate_formatter>();
                unknown_flag->add_ch('%');
                unknown_flag->add_ch(flag);
                formatters_.push_back((std::move(unknown_flag)));
                break;
            }
        }

        // Extract given pad spec (e.g. %8X)
        // Advance the given it pass the end of the padding spec found (if any)
        // Return padding.
        details::padding_info handle_padspec_(std::string::const_iterator &it, std::string::const_iterator end) {
            using details::padding_info;
            using details::scoped_pad;
            const size_t max_width = 128;
            if (it == end) {
                return padding_info{};
            }

            padding_info::pad_side side;
            switch (*it) {
            case '-':
                side = padding_info::right;
                ++it;
                break;
            case '=':
                side = padding_info::center;
                ++it;
                break;
            default:
                side = details::padding_info::left;
                break;
            }

            if (it == end || !std::isdigit(static_cast<unsigned char>(*it))) {
                return padding_info{0, side};
            }

            auto width = static_cast<size_t>(*it - '0');
            for (++it; it != end && std::isdigit(static_cast<unsigned char>(*it)); ++it) {
                auto digit = static_cast<size_t>(*it - '0');
                width = width * 10 + digit;
            }
            return details::padding_info{std::min<size_t>(width, max_width), side};
        }

        void compile_pattern_(const std::string &pattern) {
            auto end = pattern.end();
            std::unique_ptr<details::aggregate_formatter> user_chars;
            formatters_.clear();
            for (auto it = pattern.begin(); it != end; ++it) {
                if (*it == '%') {
                    if (user_chars) { // append user chars found so far
                        formatters_.push_back(std::move(user_chars));
                    }

                    auto padding = handle_padspec_(++it, end);

                    if (it != end) {
                        handle_flag_(*it, padding);
                    } else {
                        break;
                    }
                } else { // chars not following the % sign should be displayed as is
                    if (!user_chars) {
                        user_chars = details::make_unique<details::aggregate_formatter>();
                    }
                    user_chars->add_ch(*it);
                }
            }
            if (user_chars) { // append raw chars found so far
                formatters_.push_back(std::move(user_chars));
            }
        }
    };
} // namespace spdlog
